Semiconductor laser devices such as double heterostructure laser diodes are utilized in various applications such as for optical sources in fiber optic communications. In the manufacture of such devices, double heterostructures are grown and processed on a wafer substrate by, for example, liquid phase epitaxy. The wafer is then cleaved into typically solid rectangular laser bars containing many laser diodes. The laser diodes are functional at the laser bar level, and therefore electrical testing is often performed at this level prior to dicing the individual laser diodes from the bars.
Each laser bar has two end faces (facets) formed by cleaving during the cleaving process. Ultimately, laser light is transmitted through the facets, so it is important for their surfaces to remain unperturbed during handling of the laser bar. Following the cleaving operation on the wafer to form the laser bars, the facets are coated with an optical coating in a facet coating apparatus. A facet coat holding fixture is typically employed to retain the laser bar during the facet coating and also to transport the bar into and out of the facet coating apparatus.
FIG. 1 illustrates a prior art facet coat holding fixture 18 for retaining a laser bar 10 during a facet coating operation. Fixture 18 is comprised of a pair of solid rectangular fixture blades 18.sub.1, 18.sub.2 that retain laser bar 10 by sandwiching the same under a compressive force applied to side surfaces 15 thereof by a compression or clamping device 17. Laser bar 10 is a thin, solid rectangular bar with facets 14a, 14b on opposite sides, and longitudinal side surfaces 12 perpendicular to the facet surfaces. Due to its small size--e.g., typical dimensions on the order of 0.005.times.0.012.times.0.300 inches--the laser bar must be handled with extreme care to avoid damaging it. Flat side surfaces 19 of the fixture blades compress against laser bar surfaces 12 during facet coating. Once facets 14a and 14b are coated, holding fixture 18 and the retained laser bar 10 are transported out of the facet coater atop a receiving surface 13. Fixture blades 18.sub.1 and 18.sub.2 are then separated to release laser bar 10 onto surface 13 between slot S defined between the blades. The laser bar is then removed from the slot by a vacuum pick or robot arm for subsequent processing and testing operations.
The optical coating applied to the exposed facet surfaces 14a, 14b often seeps in between the side surfaces 12 of the laser bar and mating surfaces 19 of fixture blades 18.sub.1, 18.sub.2. As a result, laser bar 10 often sticks to one of the fixture blades when the blades are separated atop surface 13. An additional operation is then required to detach the laser bar from the fixture blade, e.g., manually shaking the holding fixture to loosen the laser bar or prying the laser bar from the blade with a pick. The additional operation results in a yield reduction as the laser bars tend to get damaged when pried or shaken from the fixture blades. Typically, up to 50% of the laser bars may become damaged from this operation.